Food producers and packagers are becoming more sensitive to the hygiene of their equipment and a greater focus is being placed on implementation of hygienic designs.
A conveyor generally known in the art as a “direct-drive” or “positive-drive” spiral conveyor is disclosed in U.S. Pat. No. 9,481,523B from which the following description and FIGS. 1-2 (labeled prior art) are provided.
A spiral conveyor is shown schematically in FIG. 1. The spiral conveyor includes a drive tower 10 in the form of a cylindrical drum or cage that is driven to rotate about a vertical axis 12. The rotating tower has a plurality of parallel, generally vertical drive members 14 spaced apart regularly around its periphery 16. Each drive member extends in length between the bottom 18 and the top 19 of the tower. The conveyor belt 20 follows a multi-tiered helical path around the tower. The path is defined by a helical carryway or by a carryway at the bottom and stacker plates mounted on the belt. The inside edge of the belt positively engages the drive members, which drive the belt up the tower as it rotates. The belt travels around various take-up, idle, and feed sprockets 22 as it makes its way from the exit at the top of the tower back to the entrance at the bottom. The tower 10 is mounted at its bottom to a base 24 and is rotated by a motor and gears (not shown).
Each of the drive members 14 comprises a generally vertical rail 26, which is affixed at the bottom 18 to a lower ring 27 of the drive tower 10, and a ridge 28 that protrudes outward of the rail, as shown in FIGS. 2A and 2B. The ridge is shown formed on an overlay 32 that covers the outer face 34 of the rail along just about all its length. As shown in FIG. 2C, tabs 36 hold the overlay to the rail. Instead of being formed on an overlay, the ridge could be welded directly onto the rail or formed monolithically with it.
In a lower segment 38 of each drive member, the ridge 28 includes a constant-height region 40 and a tapered region 42. A constant-height region begins at the bottom of the rail and extends upward to the tapered region. The height of the ridge 28 increases from a height h2 in the constant-height region to a maximum height h1 at the upper end of the tapered region. In other words, the distance of the ridge 28 from the vertical axis 12 (FIG. 1) of the drive tower increases from a constant distance to a greater distance at the upper end of the tapered region. The constant-height region of the lower segment 38 is angled off vertical by an angle .alpha.
The off-vertical orientation and the low height h2 of the ridge in the bottom portion of the lower segment of the drive tower facilitate the entry of the conveyor belt 20 onto the rotating tower, as shown in FIGS. 2B and 2C. The conveyor belt 20 is shown as a modular plastic conveyor belt constructed of a series of rows of belt modules 44 conventionally interconnected row-to-row by hinge rods (not shown). As the belt advances tangentially in to the rotating tower 10, one of its inside edges 46 may contact one of the ridges 28. As the belt is directed more closely toward the drive tower, the ridge eventually slides off the inside edge and into a gap 48 between adjacent belt rows. The angled orientation of the ridge in the lower segment helps guide the belt into proper engagement as it rides along its inclined helical path 50. By the time the belt reaches the tapered region 42 of the lower segment 38 of the drive members, the ridge has assumed a position just upstream of the inside edge of a belt row. In this position, the driving member is engaged with the inside edge of the belt to positively drive it along the helical path 50 without slip. In the tapered region 42, the ridge gradually increases in height to its maximum height hl. The gradual increase further aids in the transition of the belt into full positive engagement with the rotating tower, as indicated by the max-height drive member 14′.
The ridge 28 extends out to the maximum height hl in an intermediate segment 52 of each drive member 14. In the intermediate segment, the distance of the ridge from the vertical axis 12 (FIG. 1) is constant. The intermediate segment is disposed on the periphery of the drive tower just above the lower segment 38. The intermediate segment constitutes the majority of the height of the tower and, consequently, provides most of the driving engagement with the conveyor belt. The intermediate segment may be vertical as shown or slanted off vertical. Just ahead of the belt's exit from the top 19 of the tower 10, the height of the ridge tapers from the maximum height h1 to zero at the top, as shown in FIGS. 4A and 4B. The tapering occurs in an upper segment 54 of each drive member 14. The top of each rail is affixed to an upper rim 56. The decreasing height of the ridge 28, or its distance from the drive tower's vertical axis, in the upper segment allows the belt to disengage gradually and neatly from the drive members of the rotating tower.
Thus, the spiral conveyor of FIGS. 1-2 positively drives a conveyor belt without overdrive along a helical path with drive members that engage the inside edge of the belt with a ridge that varies in height from the bottom to the top of the rotating spiral drive tower.
Also referring to FIGS. 3 and 4 (labeled prior art) of U.S. Pat. No. 9,394,109, two other embodiments including a drive member 112 and cap 231 are shown.
One embodiment of the present invention provides further improvements to the conventional drive towers and drive members including, but not limited, to utilizing a hygienic design.